It is known to produce acrylic esters by carrying out a transesterification reaction between an acrylate of a light alcohol (known as light acrylate) and a heavy alcohol.
This reaction is an equilibrated catalyzed reaction with generation of light alcohol, according to the formula (I):CH2═CH—COOR1+R2—OHCH2═CH—COOR2+R1—OH
It is necessary to remove the light alcohol produced during the reaction in order to shift the equilibrium in the direction of the production of the acrylic ester.
This reaction is generally accompanied by side reactions which produce impurities which is necessary to remove for the purpose of obtaining the acrylic ester with a high purity satisfying the technical requirements related to its final use as monomer to manufacture polymers which can be used in numerous fields of application.
Furthermore, for obvious economic reasons, the economically upgradable products present in the crude reaction mixture, in particular the unreacted reactants and the catalyst, are, as far as possible, recycled within the process.
For these purposes, a separation/purification process comprising a combination of distillations, extractions and/or separations by settling is generally performed, which process is simultaneously relatively complex to carry out, in particular as a result of the presence of azeotropic mixtures, and expensive energetically.
Various transesterification processes for producing acrylic esters have already been described in the prior art.
Mention may be made, for example, of the document U.S. Pat. No. 7,268,251, in which the reaction effluent from the transesterification is treated in the following way:                either most of the desired acrylic ester is first of all separated and is subsequently isolated from the catalyst used by distillation (separation of catalyst),        or it is first of all isolated from the catalyst used by distillation (separation of catalyst) and subsequently most of the acrylic ester is separated,        and, subsequently, the compounds having a lower boiling point than that of the desired acrylic ester are separated by distillation of the mixture obtained (separation of low-boiling-point substances) and subsequently the acrylic ester is distilled (distillation in the pure state).        
This process requires the use of at least four distillation or rectification columns, including an evaporator in order to separate the catalyst, generally a titanium alkoxide.
Even if the process described in the document U.S. Pat. No. 7,268,251 relates to the manufacture of alkyl acrylates by transesterification starting from an alkyl acrylate and from an alcohol exhibiting a chain length greater by at least one carbon with respect to the alkyl chain of the starting acrylate, this process is illustrated only with the manufacture of dimethylaminoethyl acrylate from dimethylaminoethanol and methyl acrylate or ethyl acrylate in a cascade of two reactors.
It turns out that the process described in the document U.S. Pat. No. 7,268,251 is complicated to carry out on the industrial scale, as a result of the optimization of the operating conditions of the succession of the four distillation/rectification components, in order to obtain a product of high purity and a satisfactory productive output.
The document U.S. Pat. No. 6,977,310 describes a process for the continuous manufacture of (meth)acrylic acid alkyl esters from methyl(meth)acrylate and from a C2-C12 alcohol in the presence of a tetraalkyl titanate as transesterification catalyst. This process consists in subjecting the reaction mixture to a distillation under reduced pressure which separates the easily volatile compounds (unreacted reactants) and then the resulting fraction exiting at the column bottom, comprising the ester produced, the catalyst, the polymerization inhibitors and the high-boiling-point byproducts, is sent to a vacuum distillation stage which makes it possible to recover, at the top, the ester produced of high purity. This vacuum distillation stage comprises in particular a film evaporator, combined with a distillation column, for complete removal of the high-boiling-point products in the ester produced.
This process is illustrated with the manufacture of butyl methacrylate and isobutyl methacrylate, respectively from butanol and isobutanol.
The process described in the document U.S. Pat. No. 6,977,310 employs a film evaporator to prevent any decomposition of the catalyst and any formation of ethers of the alcohol reactant. This process in addition does not provide for the recycling of the catalyst.
Surprisingly, it has been found that, in the case of 2-octyl acrylate, the removal of the catalyst using a conventional boiler and not a film evaporator does not result in the formation of impurities, such as ethers or octanes.
The applicant company, seeking to solve the various problems of the abovementioned processes, has thus discovered a simplified manufacturing process for producing 2-octyl acrylate of very high purity with a high yield, while including the recycling of the economically upgradable products, such as the unreacted reactants and the catalyst, and thus exhibiting a productive output compatible with manufacture on the industrial scale.
The solution provided consists in using ethyl titanate in solution in 2-octanol or 2-octyl titanate as transesterification catalyst and in employing a purification train comprising only two distillation columns.
The present invention makes it possible in addition to produce an acrylic ester comprising carbon of renewable origin related to the use of the 2-octanol, which is an alcohol derived from plant matter.